Typical Structure

It should be appropriate to your recipient's status. 

Never skip this when writing to clients.

Always tell why you're writing unless it's absolutely clear from the context.

Make sure you form Factual Context.

One topic per email.

No open-ended questions, give options to choose from if possible.

No long discussions by email, it's better to call.

No passive unless necessary. Use the active voice, it sounds more natural.

Specify what action you expect from your recipient, if any. If you expect more than one action, consider writing an extra email. Remember: one topic per email.

Appropriate to your recipient's status.

For first communication please use full company signature. 

Next messages — short signature.

If you have an attachment, always tell your recipient what's in it.

If you talk about a document in your email, always attach or link it to save your recipient's time.

The attachment name should reflect what's inside the attachment.